Biomedical Engineering Reference
In-Depth Information
a
MWNTs
-
MWNTs
+/-
MWNTs
+
b
PEI AP-MWNT SWNT-PEI
c
SWNT-PABS or
SWNT-PEG
Control
Scheme 6.2
The effects of pristine and functionalised CNTs on neurite outgrowth and
number of growth cones in comparison with PEI. Reproduced with permission from
Hu
et al.
11
(a), Hu
et al.
14
(b), and Ni
et al.
15
(c) with permission.
The use of SWNT composite as scaffold for neuronal growth was also
reported by Haddon and coworkers.
13
On the basis of the observations
from the previous study showing that neurite outgrowth was enhanced
by using positively charged MWNTs,
11
a composite constituted of SWNTs
functionalised with PEI polymer was prepared. PEI is commonly used as
permissive substrate for neuronal growth, and it is positively charged at
physiological pH.
6
The precoating of glass coverslips with PEI in the previous
studies was necessary because the adhesion of MWNT ilms on non-coated
glass coverslips was low when the ilms were exposed to aqueous culture
medium.
5,11
Functionalisation of CNTs with PEI should increase their ability
to support neurite outgrowth, whereas the precoating of coverslips with PEI
could be eliminated.
SWNTs were functionalised using a methodology that was comparable
to the previous study.
11
PEI (branched PEI,
n
≈
20) was covalently grafted
on SWNT-COOH by amidation via oxalyl chloride activation of the carboxylic
acid functions (Scheme 6.1, path C). Then, SWNT-PEI ilms were deposited on
glass coverslips, and neuronal growth of hippocampal cells was monitored.
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